In modern telecommunications systems, glass fibers transport optical signals over thousands of kilometers with little loss or signal distortion. Although these fibers support a large bandwidth, the data rates are typically limited by the supporting electronics that produce, receive, and process the optical signals. To alleviate the demands placed upon the electronics, more processes can be done electro-optically and all-optically. One of the most fundamental components needed for such work is the optical switch or thresholder.

In this thesis a numerical model is built from basic electromagnetic theories in order to simulate the abilities of patterned active region multimode switches (PARMS) for use in optical thresholding. PARMS are active waveguide devices, which contain any number of electrically isolated active regions that can be independently biased for gain or loss. The simulation of one PARMS geometry is presented in this work, which demonstrates thresholding with a 23dB extinction ratio over a 6dB input power span.